Conventional ignition systems for internal combustion engines incorporate spark plugs located in the combustion chamber for igniting a mixture of a vaporized hydrocarbon fuel and air.
Such conventional ignition systems present a number of problems.
Because the ignition is dependent upon the spark produced by the electrodes of the spark plug, the spark itself must have a relatively high intensity of energy and must be located within the combustion chamber to initiate and to distribute the ignition throughout the combustion chamber in a way that will insure complete combustion and the required distribution of the flame front in advance of any auto ignition which might occur by localized compression or hot spots within the combustion chamber structure. Because a high intensity, high energy, high temperature spark is required, the size of the plug must be physically large; and the related electrical circuitry must have sufficient capacity for producing the high intensity spark.
The exhaust gas emissions produced by conventional internal combustion engines utilizing such spark ignition systems as described above are hard to maintain within acceptable limits, and the overall combustion efficiency and the resulting fuel economy are relatively poor.
A number of precombustion chamber systems have been proposed for producing so-called stratified charges in attempts to improve the overall combustion process, but one major drawback of most of these precombustion chamber systems has been the fact that they have relied on conventional hydrocarbon fuels for their operation. Such hydrocarbon fuels require carburetion or other control of the mixing of the fuel with the air or other oxidant within relatively narrow ranges because the combustibility range of such hydrocarbon fuels falls within a narrow band.
The use of conventional hydrocarbons fuels for precombustion chambers also produces the same problems of deposits and emissions that occur within the main combustion chamber. Thus, carbon and lead deposits on the precombustion chamber surface occur, and nitrous oxide can be formed, and unburned hydrocarbons can also be produced, because a relatively rich mixture is usually burned in the precombustion chamber to insure ignition. When relatively rich hydrocarbon fuels are used in the precombustion chamber, unburned hydrocarbons may exist in the engine exhaust even though the fuel-air mixture in the main combustion chamber is maintained relatively lean.
Because deposits are produced in precombustion chambers using hydrocarbon fuels, the precombustion chamber mechanisms themselves have been required to be relatively large. The minimum spark plug structure had to be large enough to accomodate the build-up of such deposits and still produce an effective spark. Furthermore, the precombustion chamber systems using conventional hydrocarbon fuels have required valve structure for controlling the introduction of the fuel-air mixture into the precombustion chamber, and such valve structure has conventionally taken the form of a relatively complex and bulky poppet valve arrangement which must be timed in coordination with other engine structure to control the inlet of the mixture into the precombustion chamber. The precombustion chamber systems using hydrocarbon fuels have also usually required their own carburetor, or metered fuel injection mechanism, for providing the required control over the mixture of the hydrocarbon fuel with air.
All of these features of precombustion chamber systems using hydrocarbon fuels have limited the use of such precombustion chamber systems because of the resulting complexity, size and expense of installing such systems on internal combustion engines.
In attempts to provide cleaner combustion in internal combustion engines, it has been proposed to utilize hydrogen as a fuel. Systems have therefore been proposed in which hydrogen is fed into a main combustion chamber and burned with either air or oxygen. While hydrogen is a very desirable fuel because of its clean burning characteristics, it has been impractical, to date, to use hydrogen as an internal combustion engine fuel, in place of hydrocarbon fuel, because of the cost of producing the hydrogen and the difficulty of obtaining, storing and transporting hydrogen in sufficient quantities to use as the main fuel.
It is an important object of the present invention to overcome the drawbacks of the prior art by using a highly combustible gas in a precombustion chamber which is combined with a main combustion chamber using a hydrocarbon fuel.